1. Field of the Invention
The present invention relates to a wire harness such as, for example, for vehicle or automotive applications, that includes several unitary wire harnesses each containing a plurality of electrical cables. In particular, the invention relates to colored electrical cables.
2. Description of Background Information
A typical automobile is usually wired with hundreds of electrical cables. These electrical cables are assembled into several unitary wire harnesses, each unitary wire harness being assigned to a specific car section.
As shown in FIG. 1A, such unitary wire harnesses include, for instance, an engine compartment harness W/H-1, an engine harness W/H-2 wired above the engine, a cowl harness W/H-3 wired in the dash panel (cowl panel), an instrument panel harness W/H-4, a floor harness W/H-5 wired from the front side to the rear side along the car floor, a door harness W/H-6 wired in the doors on both sides, and a roof harness (not shown in the figure) wired along the car roof.
Among them, a large-scale wire harness, such as an engine harness, an engine compartment harness, a cowl harness and an instrument panel harness, contains at least thirty to fifty, and typically one hundred to three hundred electrical cables.
In a unitary wire harness such as shown in FIG. 1B, a number of electrical cables W are bundled and taped, so as to form a trunk section and branch sections. Each end portion of the electrical cables is terminated with a connector K. Further, certain determined positions of the trunk and branch sections are mounted with fitting members such as clips to be hooked to a car body, protectors for safeguarding the harness, or corrugated tubes.
As shown in FIG. 2, an end portion of each electrical cable W is fitted with an electrical terminal T, and the latter is inserted into a corresponding terminal enclosure a, b or c, etc., formed in a connector K. During this operation, workers are susceptible of making connection errors. To avoid such mistakes, the electrical cables are differentiated by colors.
As shown in FIG. 3, a first electrical cable 5 is composed of a core wire aggregate 1 and an insulator coating 2. The latter has a plain (or solid) base color 3a (i.e. dominant or background color) in suitable colors, such as, red, blue, yellow, green, black or the like. A second electrical cable 6 has a plain base color 3a same as for the first electrical cable 5, and is further provided with, for example, two stripes 3b. The plain base colors 3a and colors of the stripes are thereby differentiated, so that workers can differentiate those electrical cables. The base color 3a may be provided in the entire insulator coating 2, or only on its external surface. By contrast, the stripes 3b are colored only on the external surface of the insulator coating.
The first and second electrical cables W may be respectively provided or spotted with identification codes 3c in suitable colors such as silver, red or black, etc., at given intervals along their length. The shape of the identification codes 3c is a function of properties such as, for example, the material and thickness of the insulator coating, the diameter of the core wire aggregate, the size of the electrical cable, etc. However, these designation identification codes 3c are not included in the different cable color markings in the sense of the invention, beside the plain base colors 3a and the striped cable colors 3b. 
As can be understood from above, many types of cable color may be used in an automobile. Further, a work bench for mounting unitary wire harnesses is usually provided with an arrangement table such as shown e.g. in FIG. 5A. The color of an electrical cable W is made to correspond to a particular terminal enclosure among a plurality of terminal receiving means of connector K, to which the cables are to be inserted, so that erroneous connections can be avoided. In other words, the cable color sets are differentiated as a function of the destination of the electrical cables W (e.g. electrical cables W destined for a circuit). A circuit can thus be connected by inserting a given colored cable into the corresponding terminal enclosure. When the correspondence is erroneous, a desired circuit cannot be constructed.
One difficulty of harness arrangement resides in the fact that connectors in a vehicle or an automobile are initially joined to existing electric parts, for example, electronic control units and junction boxes, and the connections of unitary wire harnesses must be adapted to these situations. Further, a unitary wire harness may be connected between several connectors by crossing with other partially-connected wire harnesses, so that the electrical cables of one harness intertwine with those of other harnesses, and it is often difficult to attribute these cables to their terminal receiving elements in a consistent manner.
The electrical cables W to be engaged into terminal receiving means, in the form of enclosures or receptacles a, b and c etc. of a connector K, are identified by the corresponding cable colors. As the number of terminal receiving elements multiplies, the types of color to be used must also be multiplied so as to avoid misconnections.
Recent years have witnessed the multiplication of the number of terminal receiving elements formed in each connector K. Nowadays, its number sometimes reaches forty. Accordingly, many types of cable color are now being used. For instance, thirteen base colors are combined with different stripe colors, yielding, for example, forty six kinds of cable color.
However, when the cable colors are multiplied, the electrical cables produced become much more expensive. In addition, when the cables"" size is small, the width of the stripe colors and that of the base colors become undistinguishable. As a result, it becomes difficult not only to identify the base colors, but also to distinguish the stripe colors from the base colors. This makes the workers"" task particularly burdensome.
The present invention thus has for object to reduce the types of cable color required without risk of connection errors, to reduce the manufacturing costs of cables, and to alleviate fatigue on workers due to color differentiation efforts. To this end, there is provided a method for determining a critical number of colors for the electrical cables constituting a wire harness such as, for example, a vehicle or an automotive wire harness. The wire harness includes a plurality of unitary wire harnesses to be engaged with a given number of connectors. Each of the unitary wire harnesses contains a plurality of electrical cables which respectively have a different color marking and include an electrical terminal attached to at least one end thereof, and each of the connectors includes a plurality of terminal receiving elements respectively configured to receive a corresponding electrical terminal, so that each of the unitary wire harnesses can be engaged with a given number of connectors. The above method further comprises:
selecting a critical unitary wire harness among the plurality of unitary wire harnesses;
determining the critical number of different color markings to be contained in the critical unitary wire harness on the basis of the empirical formula:
R=A/B+C/Bxe2x80x83xe2x80x83(I)
xe2x80x83in which R is the critical number of different color markings; A is the total number of electrical cables contained in the critical unitary wire harness; B is the total number of connectors to be engaged with the critical unitary wire harness; and C is the total number of terminal receiving elements contained in all of the connectors to be engaged with the critical unitary wire harness; and
setting the total number of different cable color markings necessary for each of the plurality of unitary wire harnesses to be equal to or less than the critical number of different color markings.
Selecting a critical unitary wire harness may include choosing a unitary wire harness containing either the greatest number of electrical cables or the greatest number of connectors.
Determining the critical number of different color markings may include multiplying member R by a number equal to at least about 1.5, when C/B is less than about 9.
Preferably, the above number equal to at least about 1.5 is a number between about 1.5 and about 2.0, inclusive.
Further, determining the critical number of different color markings may include rounding up R to the nearest higher integer value, when said member R is a decimal number.
Typically, the above different color markings may include a plain base color and/or a striped base color.
Preferably, the different color markings are composed solely of plain base colors.
Preferably yet, the different color markings include thirteen types of color at the maximum.
Typically, all of the different color markings used for a specific connector are different from one another, or the terminal receiving elements in a specific connector are arranged such that either the same different color markings are not placed in adjacent positions, or are placed in different sub-classes which are defined for the terminal receiving elements.
Further, selecting a critical unitary wire harness may include choosing a unitary wire harness containing at least thirty electrical cables.
Alternatively, the different color markings may further be provided or spotted with identification codes along the length of the electrical cables at given intervals.
The invention also relates to a system for determining a critical number of colors for the electrical cables constituting a wire harness such as, for example, for automotive applications, the wire harness including a plurality of unitary wire harnesses to be engaged with a given number of connectors, each of the unitary wire harnesses containing a plurality of electrical cables which respectively have a different color marking and include an electrical terminal attached to at least one end thereof, and each of the connectors includes a plurality of terminal receiving elements respectively configured to receive a corresponding electrical terminal, so that each of the unitary wire harnesses can be engaged with a given number of connectors. The above system includes:
a selector that selects a critical unitary wire harness among said plurality of unitary wire harnesses;
an element that determines the critical number of different color markings to be contained in said critical unitary wire harness on the basis of the empirical formula:
R=A/B+C/Bxe2x80x83xe2x80x83(I)
xe2x80x83in which R is the critical number of different color markings; A is the total number of electrical cables contained in said critical unitary wire harness; B is the total number of connectors to be engaged with said critical unitary wire harness; and C is the total number of terminal receiving elements contained in all of the connectors to be engaged with said critical unitary wire harness; and
a device that sets the total number of different cable color markings necessary for each of said plurality of unitary wire harnesses to be equal to or less than said critical number of different color markings.
In the above system, the selector that selects a critical unitary wire harness includes a device that chooses a unitary wire harness containing either the greatest number of electrical cables or the greatest number of connectors.
Further, the element that determines the critical number of different color markings comprises a device that multiplies member R by a number equal to at least about 1.5, when C/B is less than about 9.
Typically, the different color markings include a plain base color and/or a striped base color.
Suitably, the different color markings include thirteen types of color at the maximum.
The invention further may include a wire harness for vehicle or automotive applications, including a plurality of unitary wire harnesses to be engaged with a given number of connectors, each of the unitary wire harnesses containing a plurality of electrical cables which respectively have a different color marking and include an electrical terminal attached to at least one end thereof, the unitary wire harnesses being configured to be engaged with the connectors including a plurality of terminal receiving elements for receiving a corresponding electrical terminal. The above wire harness includes:
a critical unitary wire harness selected among the plurality of unitary wire harnesses;
a critical number of different color markings to be contained in the critical unitary wire harness, determined on the basis of the empirical formula:
R=A/B+C/Bxe2x80x83xe2x80x83(I)
xe2x80x83in which R is the critical number of different color markings; A is the total number of electrical cables contained in the critical unitary wire harness; B is the total number of connectors to be engaged with the critical unitary wire harness; and C is the total number of terminal receiving elements contained in all of the connectors to be engaged with the critical unitary wire harness; and
a necessary total number of different cable color markings determined for each of the plurality of unitary wire harnesses, which are equal to or less than the critical number of different color markings.
The above critical unitary wire harness may include a unitary wire harness containing either the greatest number of electrical cables or the greatest number of connectors.
Preferably, the critical number of different color markings includes member R multiplied by a number at least equal to about 1.5, when C/B is less than about 9.
Preferably yet, the different color markings include a plain base color and/or a striped base color and include a maximum of thirteen types of color.
The required number of different color markings for the invention are related to the number of electrical cables, the number of connectors, and the number of terminal receiving elements contained in a connector. These numbers are therefore taken into consideration in the above formula. The critical number of different color markings is defined for a particular unitary wire harness, so that the electrical cables, to be engaged into the terminal receiving elements of one connector, do not have a same cable color markings. The number of cable color markings for the other unitary wire harnesses is then limited to be equal to or less than the above critical number.
The first member A/B of the above empirical formula gives the mean value of electrical cables per connector. When this mean value increases, the critical number of different color markings also tends to increase.
The second member C/B of the above empirical formula gives the mean value of terminal receiving elements per connector. When this mean value increases, the critical different color markings also tends to increase.
When connectors having a small number of terminal receiving means, rather than those having a large number thereof, are preferably used, both mean values decrease. Conversely, when connectors having a large number of terminal receiving elements are preferably used, the number of different color markings is required to be greater than the mean values. In order to solve such problems, the critical number R is multiplied by a correction factor for security or safety of at least about 1.5, preferably a number chosen between about 1.5 and about 2.0, inclusive. This correction factor is obtained empirically, a value of less than about 1.5 or over about 2.0 being found not to be entirely satisfactory.
In other words, when the mean number of terminal receiving elements per connector is at least about 9, the critical number of different color markings R is not multiplied by a number of at least about 1.5, and, when the mean cavity number per connector is less than about 9, the critical number R is multiplied by a number equal to at least about 1.5.
In some unitary wire harnesses, there are employed many large-scale connectors (with a great number of terminal receiving elements), which can thus engage with a large number of electrical cables. In such a case, once the critical number of different color markings for the unitary wire harness containing the largest number of electrical cables is determined, this critical number is also sufficient to distinguish the different color markings for the other unitary wire harnesses. Accordingly, all the different color markings used in an entire system such as, for example, a vehicle or an automobile can thus be kept below the critical number of different color markings.
Instead of the greatest number of electrical cables as mentioned above, the greatest number of terminal receiving elements may be used for determining the critical unitary wire harness for the above calculation. Likewise, when the connector to be engaged with a unitary wire harness includes a mean number of terminal receiving elements of at least nine, the number of different color markings for all the unitary wire harnesses may be equal to or less than the critical number R.
Normally, the unitary wire harness containing the greatest number of electrical cables is engaged with the largest-scale connector (having the greatest number of terminal receiving elements). Sometimes, however, a unitary wire harness not containing the greatest number of electrical cables may be engaged with the largest-scale connector. However, as mentioned above, electrical cables are differentiated by many colors in order to avoid connection errors to a large-scale connector. Accordingly, in the above case, the critical number of different color markings of formula (I) is calculated on the basis of the unitary wire harness to which the largest-scale connector is engaged.
Further, by reducing the types of different cable color markings, all the electrical cables wired in the entire system such as, for example, a vehicle or an automobile may be provided or painted in a base color without having to add stripes.
In this manner, the stripe-painting process can be obviated, and the cable manufacturing costs are drastically reduced.
In particular, in the small-sized electrical cables, the cable colors can be identified more easily when they are not striped. The use of xe2x80x9cstripelessxe2x80x9d cable colors thus alleviate the burden on workers.
However, the plain base colors and the base colors striped in another color may be used jointly, and their total cable colors may be brought to a number equal to or less than the critical number of different color markings.
The unitary wire harnesses containing the number of different color markings equal to or less than the value obtained by formula (I) may include a total of at least thirty, at least fifty or at least one hundred electrical cables, the last being the most common.
In particular, the engine harness, the engine compartment harness or the instrument panel harness contains a great number of electrical cables. The number of their different color markings is at most the critical number obtained from the above formula.
The roof harness or the door harness contains a smaller number of electrical cables, and consequently a smaller number of different cable color markings than that obtained from the formula above.
Also in such cases, the unitary wire harness containing the greatest number of electrical cables may be taken as critical harness, and the critical number of different color markings may be calculated. As already mentioned, this critical number of different cable color markings may also be applied to unitary wire harnesses having a smaller cable number. Likewise, the number of different color markings used in the entire vehicle can be calculated from formula (I).
In most commercial automobiles, the critical number of different color markings thus calculated amounts to a value ranging from 12 to 14, especially to 13.
Accordingly, according to the present invention, the number of different color markings used for the entirety of the vehicle""s electrical cables is determined to be 12 to 14 types at the most, preferably 13 types. The above number of different color markings for electrical cables may be composed of plain base colors only, or may be a mixture of plain base colors and striped base colors.
However, as the critical number of different color markings is reduced e.g. to 13, the complete set of cable colors may be constituted by the plain base colors only. In other words, all the electrical cables wired in an automobile are provided painted with thirteen types of plain base colors.
In another embodiment, the electrical cables in plain base colors or striped base colors may further be spotted with markings formed at given intervals along the length of the cable. In such a case, the cable colors with markings are not counted as different color markings within the meaning of the invention.